1. Field of the Invention
The present invention relates to an apparatus which uses a reaction attended with gas absorption and release in a gas absorption and release substance such as a hydrogen storage alloy or which uses a reaction attended with heat using the function of gas absorption and release or heat absorption and release in a refrigerator or the like, and further relates to a method of controlling the apparatus.
The present application is based on Japanese Patent Application No. 2000-252027, which is incorporated herein by reference.
2. Description of the Related Art
Because a gas absorption and release substance such as a hydrogen storage alloy produces a reaction of absorption or release of a gas such as hydrogen attended with heat absorption and generation, various kinds of systems using this reaction have been heretofore proposed.
For example, a hydrogen storage alloy produces absorption and release of heat when the hydrogen storage alloy absorbs or releases hydrogen. Hence, there have been proposed apparatuses in which absorption or release of hydrogen is performed by a pressure or temperature operation so that air-conditioning, refrigeration or heat recovery is made by using the heat generated in the absorption and release of the hydrogen. There have been also proposed apparatuses in which hydrogen storage, conveyance, recovery, purification or the like are performed by using the absorption and release of heat.
Referring to FIGS .4 and 5, the gas absorption and release apparatus meeting the aforementioned purpose will be described. as supply unit 4 is connected to a gas absorption and release container 1 containing a gas absorption and release substance through an electromagnetic valve 2 and a gas supply passage 3. A gas-using unit 7 is connected also to the gas absorption and release container 1 through an electromagnetic valve 5 and a gas release passage 6.
A heat medium introduction passage 8 and a heat medium discharge passage 9 are further connected to the gas absorption and release container 1. A cooling heat medium supply unit 12 is connected to the heat medium introduction passage 8 through a pump 10 and a cooling heat medium supply passage 11. A heating heat medium supply unit 15 is connected also to the heat medium introduction passage 8 through a pump 13 and a heating heat medium supply passage 14. On the other hand, a cooling heat medium return passage 17 is connected to the heat medium discharge passage 9 through an electromagnetic valve 16. A heating heat medium return passage 19 is connected also to the heat medium discharge passage 9 through an electromagnetic valve 18. Incidentally, the electromagnetic valves 2, 5, 16 and 18 and the pumps 10 and 13 are subjected to centralized control by a control unit 20.
In the aforementioned apparatus, when gas is absorbed into or released from the gas absorption and release substance, the electromagnetic valves and the pumps are controlled by the control unit 20 in accordance with the operation of gas absorption/release.
That is, the gas absorption and release substance has limits in quantity of gas absorption and release. In the aforementioned apparatus, therefore, absorption or release is stopped when absorption or release reaches its limit respectively, and, at the same time, the operation is switched over between absorption and release so that gas absorption and release are repeated.
In the related art, the judgment as to whether or not gas absorption/release into/from the gas absorption and release substance reaches its limit is made in consideration of the predicted absorption/release capacity (the quantity or rate of absorption/release) of the substance. For example, there has been used a method in which time is measured from the start of absorption or release and judgment is made that the absorption or release reaches its limit when the measured time reaches a setting value, or a method in which a gas flow meter 21 is disposed in the absorption/release passage 6 or the like as shown in FIG. 5, and judgment is made that the absorption or release reaches its limit when the gas flow rate, that is, the quantity of gas absorption/release reaches a setting value.
According to the related-art judgment method, if the actual absorption/release capacity of the gas absorption/release capacity exceeds a setting value (predicted value), switching-over is performed without making the full use of the absorption/release capacity of the gas absorption and release substance respectively. Hence, absorption and release are repeated by a larger number of times than required. Hence, the absorption and release substance is apt to deteriorate rapidly. Moreover, sensible-heat loss caused by repetition of heating and cooling of the container containing the absorption and release substance increases, so that energy efficiency becomes poor. On the other hand, when the actual absorption/release capacity is reduced to be smaller than the setting value with the deterioration of the gas absorption and release substance, the operation is not switched over between absorption and release even in the case where the capacity exceeds its limit. The reason is as follows. That is, a blank period in which the capacity cannot be fulfilled is generated, so that the apparatus cannot make the full use of its capacity (the quantity of gas recovery, gas supply, or heat absorption or release per unit time, and so on). Moreover, wasteful motive power is generated for transporting the heating/cooling heat medium during the blank period.
The present invention is devised upon such circumstances and an object thereof is to provide a gas absorption and release apparatus using a gas absorption and release substance in which a gas absorption or gas release is switched over accurately in accordance with the actual absorption/release capacity of the gas absorption and release substance to thereby make it possible to perform the operation efficiently, and to provide a method of controlling the gas absorption and release apparatus.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a method of controlling a gas absorption and release apparatus using a gas absorption and release substance in which the gas absorption and release substance is heated/cooled by a high-temperature/low-temperature heat medium and a gas absorption/release reaction attended with heat absorption/generation is produced in the gas absorption and release substance, the method comprising the steps of: detecting a gas pressure at the time of gas absorption/release; and judging a limit of gas absorption/release on the basis of comparison between the detected pressure and a predetermined setting pressure.
According to a second aspect of the present invention, preferably, in a method of controlling a gas absorption and release apparatus using a gas absorption and release substance as stated in the above first aspect, judgment of the limit of gas absorption is made when the pressure detected at the time of gas absorption is higher than the setting pressure for gas absorption.
According to a third aspect of the present invention, preferably, in a method of controlling a gas absorption and release apparatus using a gas absorption and release substance as stated in the above first or second aspect, judgment of the limit of gas release is made when the pressure detected at the time of gas release is lower than the setting pressure for gas release.
According to a fourth aspect of the present invention, preferably, in a method of controlling a gas absorption and release apparatus using a gas absorption and release substance as stated in any one of the above first through third aspects, judgment of the limit of gas absorption/release is made when relation between the detected pressure and the setting pressure on the basis of a result of the comparison is retained for a fixed period.
Further, according to a fifth aspect of the present invention, there is provided a gas absorption and release apparatus using a gas absorption and release substance, comprising a gas absorption and release container for receiving the gas absorption and release substance airtightly, a heat medium supply means for selectively supplying a high-temperature/low-temperature heat medium to the gas absorption and release container to heat/cool the gas absorption and release substance, a gas supply means for supplying a gas to the gas absorption and release container to make the gas absorption and release substance absorb the gas, and a gas transportation means for taking out a gas released from the gas absorption and release substance, from the gas absorption and release container and transporting the gas to a gas-using portion, wherein the apparatus further comprises one pressure detection means provided in at least one place among a gas supply passage between the gas supply means and the gas absorption and release container, a gas-receiving space in the gas absorption and release container, and a gas transportation passage in the gas transportation means for detecting a gas pressure, a judgment portion for comparing the pressure detected by the pressure detection means with a predetermined setting pressure so as to judge a limit of gas absorption and release on the basis of the comparison, and an absorption and release control portion for outputting a control signal to switch gas absorption and release to the heat medium supply means, to the gas supply means and to the gas transportation means on the basis of a result of the judgment in the judgment portion.
Incidentally, in the present invention, gas absorption and release are performed by use of a gas absorption and release substance. Although a typical example of the substance is a hydrogen storage alloy, any suitable material may be used if the material can make a gas absorbing and releasing reaction so that heat absorption or release occurs consequently. For example, a material capable of adsorbing and desorbing a gas as an adsorbent or a material capable of absorbing and releasing a gas by a reaction can be used. That is, the xe2x80x9cgas absorptionxe2x80x9d includes gas adsorption and the xe2x80x9cgas releasexe2x80x9d includes gas desorption. The material may be a material capable of absorbing and releasing a gas reversibly. Examples of this type of material are activated carbon, carbon fiber, zeolite, activated alumina, and soon. Alternatively, the material may be a material capable of absorbing and releasing hydrogen gas reversibly by a chemical reaction. The aforementioned hydrogen storage alloy is an example of the material of this type.
Any suitable gas in accordance with the kind of the substance is selected as the gas absorbed and released by the aforementioned substance. For example, hydrogen gas is selected for the hydrogen storage alloy.
The gas absorption and release substance absorbs and releases a gas by being heated and cooled through a high-temperature/low-temperature heat medium. Generally, the gas absorption and release substance is contained in a gas absorption and release container airtightly. Gas absorption and release passages are connected to the container. One pipe or the like may be used both as an absorption passage and as a release passage. Alternatively, an absorption passage and a release passage may be provided separately.
Further, the heat medium is introduced into the container so that heat exchange can be performed between the heat medium and the gas absorption and release substance. The configuration of a heat medium receiving space and a heat medium moving passage in the container is not particularly limited and any configuration may be used so long as heat exchange can be efficiently performed between the heat medium and the gas absorption and release substance.
The kind of the heat medium as to whether a high-temperature heat medium or a low-temperature heat medium is not particularly limited in the present invention and can be determined suitably in consideration of the temperature for heating/cooling, or the like. The method of supplying the heat medium is also optional.
Further, the gas to be absorbed to the gas absorption and release container is generally supplied from a gas supply means, and the gas released from the gas absorption and release container is sent to a gas-using portion. A reservoir tank for reserving a gas can be used as the gas supply means. The gas-using portion can be supposed to have various purposes. Incidentally, the gas absorption and release apparatus is to use a gas or is to use heat absorption and release caused by gas absorption and release.
Further, another gas absorption and release apparatus making a pair with the gas absorption and release apparatus according to the present invention may be further provided as the gas supply means or as the gas-using portion.
In the present invention, a gas pressure is detected at the time of gas absorption and release. The detection may be performed either at the time of gas absorption or at the time of gas release or the detection may be performed both at the time of gas absorption and at the time of gas release. In order to perform absorption and release accurately, it is preferable that the gas pressure is detected both at the time of gas absorption and at the time of gas release.
The detection of the gas pressure is preferably performed in a position near to the gas absorption and release substance so that the atmospheric pressure of the gas absorption and release substance can be measured. The gas pressure is preferably detected in a gas-receiving space disposed in the gas absorption and release container. In the present invention, however, the method of detection is not limited thereto. For example, the gas pressure may be detected in a gas supply passage between the gas supply means and the gas absorption and release container or in a gas-transportation passage in a gas transportation means. Alternatively, the gas pressure may be detected in a plurality of positions among the aforementioned positions.
The setting pressure to be compared with the detected gas pressure can be set in advance while the gas pressure which appears when the capacity of the gas absorption and release substance reaches its limit is predicted. The limit of the capacity can be determined with the state, as a reference, in which gas absorption or release is little performed, or with the state, as a reference, in which gas absorption or release is reduced greatly. The degree thereof can be determined suitable. The condition for estimating that the capacity reaches its limit is determined to be used for comparison between the detected gas pressure and the setting pressure. For example, at the time of gas absorption, the condition that the detected pressure is higher than the setting value can be used for judging the limit of gas absorption. On the other hand, at the time of gas release, the condition that the detected pressure is lower than the setting value can be used for judging the limit of gas release.
Further, in the judgment of the limit, it is preferable that the detected pressure""s arrival at the limit is judged when the aforementioned condition is kept for a predetermined period, because misjudge owing to disturbance or the like must be avoided and because the gas absorption and release reaction of the gas absorption and release substance is completed in a certain time after the detected pressure""s arrival at the setting value. Although it is difficult to determine the retention time uniquely because the retention time depends also on the heat exchanging performance of the container with the absorption and release substance, the gas absorption and release rate of the absorption and release substance and the controlling characteristic of the system, the retention time can be determined suitably in consideration of the aforementioned performance or the like. For example, the appropriate time required for completing the gas absorption and release reaction of the gas absorption and release substance after the detected pressure""s arrival at a setting value or the time required for disturbance is measured in the system in advance so that the retention time can be determined on the basis of the measured time.
In the controlling method according to the present invention, after the limit of gas absorption or release is judged in the aforementioned manner, gas absorption or release is stopped and the operation is switched over between gas absorption and gas release if it is desired. The series of operations can be performed in the control portion. The subjects to be controlled vary in accordance with the configuration of the apparatus because the subjects are necessary for switching over between gas absorption and gas release. Generally, the subjects to be controlled are valves provided in the gas supply and discharge passages, the supply portion of the gas supply unit, valves provided in the heat medium supply means, pumps as transportation means, etc.
According to the present invention, when a gas is absorbed and released, the limit of gas absorption and release can be judged at an appropriate time in accordance with the state of the gas absorption and release substance. Hence, the progress of the deterioration of the gas absorption and release substance can be suppressed. In addition, generation of wasteful motive power, or the like, can be prevented, so that efficient control can be made.